1. Field of Invention
This invention relates to seal structures and more particularly to sealing structures in which the sealing surface is sealed by the application of a pressing force on a gasket inserted in a groove formed in a flange facing the sealing surface.
2. Prior Art
In automobile engines, the cylinder head 8 and the rocker arm cover 10 are generally designed as shown in FIG. 1. Specifically, a seal structure is usually adopted in which the sealing surface is sealed by the application of a pressing force in a direction roughly perpendicular to the sealing surface on a gasket inserted in a groove formed in a flange facing the sealing surface. This has the conventional seal structure as shown in FIG. 2. In the figures, the head cover or rocker arm cover 10 is equipped with a flange 16. A groove 12 that runs around the entire periphery of the rocker arm cover 10 is performed in the flange 16 for the purpose of holding a gasket 12. This gasket 12 is roughly oval shaped in cross-section. In this conventional seal structure, the seal surface 18 (i.e., the portion of the surface of the cylinder head 8 that is sealed) is sealed by applying a pressing force in a direction roughly perpendicular to the sealing surface 18 by the rocker arm cover 10 (as shown in FIG. 3). Such conventional sealing structures, however, suffer from certain drawbacks. When the rocker arm cover 10 is tightened down with a great deal of force, the sealing surface side of the gasket 12 is caused to protrude outward in a lateral direction as indicated by the arrows A. Accordingly, the seal area becomes excessively large so that the pressing force acting on the sealing surface becomes insufficient and which in some cases results in a loss of the ability to prevent leakage from the inside of the cylinder head.